I've been raising chickens for a while now, first in Brazil where I grew up, now here in Texas where the winters are much colder than where I grew up but certainly not as cold as the more northern states.
The first few years I had to adjust to keeping my hens happy in the winter time. I learned a few tricks that I'm going to share with you that have worked for me in my chicken flock.
1. Extra bedding. Chickens won't lay as many eggs in the winter due to cold and less light. First problem we can help solve is the cold. With extra bedding in their coop it will help them stay warm. The manure will heat up and as long as you have plenty of bedding, hay or shavings, it will absorb the moisture caused by the chickens and will heat up and help keep the temperature warmer. If you give them hay or straw, sometimes they like to scratch in that and find seeds or bugs that they can enjoy as a special treat.
2. Extra light. Hens lay more eggs when the days are longer. I've found that adding a light to the coop helps them lay more eggs. What has worked best for me is to turn the light on in the coop right before dark and leave it on until bedtime. This does involve an extra trip outside in the cold and dark but it causes the chickens to eat more, be awake longer and think they ought to be laying more.
3. Extra green feed. Part of the reason hens lay so well in the spring and summer is all the green treats they can pick at and the extra protein. One way that I've found that makes them happy and helps them lay more eggs is to feed them green scraps. We grow sprouts especially for the hens in the winter time and they love it. They always seem to lay better a few days after their sprout treats. We also continue to give them the scraps from what we cook in the kitchen and anything green from the garden. (Yes we do grow things in the winter!)
Summary: Keep them as warm as you can, give them extra light, feed them extra greens and protein and they should keep laying eggs even through the winter!